Alumina sintered bodies have heretofore been used for a seal, a slide ring, a pump, a piston, and the like that are required to have an abrasion-resistant property.
For example, Patent Document 1 describes use of the alumina sintered bodies for a radial or axial slide bearing in a centrifugal pump, a slide ring in a rotatable mechanical seal, and a piston or a piston casing for a reciprocating pump.
The alumina sintered body described in Patent Document 1 contains 1.2 to 6 mass % of Fe2O3, 0.1 to 0.3 mass % of MgO, 0.1 to 0.6 mass % of SiO2, 2.5 mass % or less of Mn2O4, 1.1 mass % or less of Cr2O3, and 90 to 98 mass % of Al2O3 as a residual part, and has an average grain size of the crystalline component is 5 to 15 μm, and the rate of a glass phase based on Fe2O3 is 2 to 10 mass % with respect to the Al2O3 content.
Also, as a sintered body formed of fine alumina grains and coarse alumina grains, there has been known an inorganic sintered ultraprecise measurement table obtained by sintering a mixture of coarse grains consisting mainly of corundum and having a grain diameter of 0.2 to 5 mm and fine grains having a grain diameter of 5 μm or less at a temperature of 1300 to 1500° C. so as to attain a porosity of 0.1 to 20% and performing polishing processing to flatten a working surface (see Patent Document 2).
Also, there has been known a manufacturing method for heat shock resistant alumina/zirconia-based firing jig, which is obtained by forming a molded article by mixing 20 to 70 mass % of coarse alumina grains having an average grain diameter of 30 to 200 μm, 20 to 70 mass % of fine alumina grains having an average grain diameter of 1 to 5 μm, and 5 to 30 mass % of zirconia grains having an average grain diameter of 5 to 30 μm, firing the molded article, and finely dispersing the zirconia grains in an aluminous substance binding the coarse alumina grains (see Patent Document 3).    Patent Document 1: Japanese Patent No. 3431179    Patent Document 2: Japanese Examined Patent Publication No. 3-31664    Patent Document 3: Japanese Patent No. 3949950